Thermionic tube



July 29, 1930. E LUBCKE 1,771,717

THERMI ON I C TUBE Filed Feb. 19, 1927 INVENTOR Pmmahynmao UNITED STATESPATENT OFFICE mar 1mm, 01' BIBLINBS'IAM, Gm, LSSIGHOB TO 51MB 6: mm,AKI'IENGEBELLSOHAF'I, O! BIEKINSSTADT, mum BERLIN, am, A.

CORPORATION O1 Gm 'ramromc ma Application fled I'ebraary 19, 1887,lerlal Io. 189,431, and in Germany February 88, 1989.

This invention relates to a thermionic tube and more particularly to atube using an arc as a source of electrons.

Discharge tubes for the amplification of p electrical currents and theproduction of electrical oscillations are known in whichthe incandescentfilament is replaced by a spontaneous or unassisted arc discharge. Inthese devices, one disturbing element is that the current flowing acrossthe arc is not constant, with the result that current surges or rushes(impulses) are super osed upon the are current, and these maye of such avalue that the use of the are as an electron source for many purposesbecomes questionable.

It is an object of this invention to avoid variations in the strength ofthe arc current. According to the present invention, a distinct electronsource is provided. above the filament go of the are discharge. For thispurpose, for instance, one or more heated electrodes may be disposedabove the surface of the main cathode, or else one or more discharges(arcs) may be maintained. Another scheme would be to use the cathodeitself as a base for the auxiliary arcs.

The accom anying drawing shows two embodiments o' the basic idea of theinvention by way of example. 7

Figure 1 is a section through a tube utillzing a mercury are, having anauxiliary cathode of the filament type, and

Figure 2 is a section through a similar tube with another type ofauxiliary cathode.

Referring 'to the embodiment shown in Figure 1, 1 is the main cathode, 2the main anode, 3 the control grid, and 4 the amplifier anode. In orderto insure as great as possible a constancy of the arc current flowingbetween cathode 1 and anode 2,a hot'filament 6 supplied from batte thecathode surface. f course, in lieu of onl one hot filament, a pluralitythereof co d be provided, and these should then be uniforml distributedaround the periphery of the tu 7 is a screen which is designed toprevent precipitation or condensation of droplets of'mercury upon thefilament 6. To insure abundant electron emission from fila- M ment 6,the same in well known manner may 5 is disposed above p be coated with afilm of oxide or thorium.

Under certain circumstances, it may also be suitable to use filamentscoated with hydrides of alkaline earths. Figure 2 shows anotherembodiment of the lnvention. 8 is a discharge vessel, 9 the maincathode, 10 the main anode, 11 the control End, and 12 the amplifieranode. In the midle of cathode 9 is secured a pin 13 which is made ofzirconium or hafnium oxideQ But 1t may also have the composition of andbe made like the glowers used in Nernst lamps. The top part of said pin13 may be electrically heate by heater spiral 14. If by the aid of thespiral 14 the end of the pin 13 is caused to incandesce, then an arcW111 be set up in the direct neighborhood of the pin, emission beingautomatically regulated by its own current. The end of pin 13 may becoated with oxldes of alkaline metals, h drides of alkaline earthmetals, and the H e.

The operation of the device as here disclosed is probably predicatedupon the fact that the electrons or ions issuing from the hot' filamentor at the auxiliary discharge partly compensate the s ace-charge at thecathode, or upon the fact t at the same diminish the requisite enerexpenditure normally covered or supplie by the arc discharge b causinthe detachment of electrons from t e cath c.

Having thus described my invention, what I claim 19: t

1. In an electron discharge device, an anode an auxiliary anode, agrid,a primary cathode consistin of liquid mercury, and a secondary catho c,said secondary. cathode comprisin a pin of electron-emissive materialexten g through and above the primary cathode, and a heating coil withinsaid 2. In an electron discharge device, a primary anode, a secondaryanode, a grid, a primary cathode compilrising liquid mercury, and asecondary cat ode comprising an oxide in of electron-emissive materialextending through and above the li uid mercury, and a heating coilwithin t e pin to cause the said pin to incandesce.

- ERNST LUBGKE.

